I'll Be Your Actin If You'll Be My Myosin
by smartcat
Summary: A lesson on muscle contraction Naruto will never forget. SasuNaru.


**I don't know if this should be considered as crack or what. But what gave birth to this particular story was me trying to study for my Physiology exam.**

**Anyways, I hope you guys like it…and understand it for that matter, because if you_ do_ understand it, I doubt you'll ever forget how muscle contraction works XD**

**Warning: Sex. Anyone confused? No? Good.**

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I'll be your Actin if you'll be my Myosin

~~~~~'''''~~~~~

"Argh, damn it!" Naruto growled out as he slammed his Biology notebook against the polished wood table, "I still can't fucking remember this stupid sliding filament theory!"

Sasuke rubbed at his temples furiously, trying to somehow keep his anger in check and squash that growing desire to grab the blond by the neck and shake. Shake _very _hard.

His boyfriend was an idiot.

He knew that.

"Face it, Sasuke," Naruto sat down glumly in his chair, arms crossing over his chest, "I'm going to bomb tomorrow's exam."

"You're not going to bomb it," Sasuke said in frustration, "Your parents didn't leave me here with you for that. I'll make sure you pass."

"How?" Naruto cried out, eyes narrowing on the object of his disdain.

His notebook just sat there quietly, mocking the hell out of him.

The Uchiha sighed.

How…that was the million dollar question.

How was _he_ supposed to make Naruto remember the thirteen steps of the sliding filament theory of muscle contraction?

He had tried almost everything!

Flash cards.

Memory games.

Making the damn dobe rewrite his notes ten times.

Nothing conventional was working!

Suddenly Sasuke's expression went blank.

Naruto, noticing the pensive look that came over his lover's face, unfolded his arms. Poking the statuesque Uchiha in the shoulder, the blond gazed into Sasuke's eyes questioningly.

Instantly the cool, inky black gaze of Sasuke Uchiha focused in on one Naruto Uzumaki.

"Naruto," Sasuke said evenly, eyes boring into spheres of blue, "We're going to have sex."

"What?"

"Sex."

"Yeah, I got that part," the blond scratched his head, "But now? You're my tutor too…aren't you supposed to be encouraging me to study instead of...well, you know…"

"Oh believe me," Sasuke smirked, grabbing the blond by the collar, "We _are _going to be studying."

"Really?" Naruto said, starting to get excited. If Sasuke could somehow make him remember the thirteen steps of muscle contraction, he might just pass biology!

Standing up from his chair, Sasuke pulled Naruto up with him, eyes locking together. Then slowly leaning in, the Uchiha brought his lips down, pressing them firmly against the blonde's. Naruto eagerly parted his lips, coaxing Sasuke into doing the same, but the raven pulled away, his eyes already beginning to glaze over with lust and desire.

"That," he said, "Is the first step of muscle contraction."

"Huh?" Naruto stopped, wondering if maybe he missed something.

"How do you feel?" Sasuke pressed, "You excited yet?"

"Well duh!" The blond rolled his eyes, "You said we're going to have sex and then you kissed me. Excited is an understatement."

Sasuke smirked, "Step number one, the nerve signal arrives at the neuromuscular junction."

"…"

"This kiss," Sasuke sighed, "Think of that as the nerve signal. When I kissed you, that feeling you got went straight to yo –"

"I know where it went!" Naruto interrupted, red faced. "Don't need to say where…"

"Hn."

Cupping Naruto's cheek, Sasuke leaned in again, hungrily kissing his blond and this time, opening his mouth. Tongues instantly collided with one another as both boys hungrily tried to win long fought over territory. Naruto moaned as Sasuke's tongue slid across his lip and entered his mouth, crossing over teeth to rub against his tongue. Right as he was about to weave them both together, the Uchiha pulled away.

Panting, the blond looked at his boyfriend crossly, "Now what?"

"Steps two...and three." Taking a deep breath, the raven stared into Naruto's confused face.

"How exactly…?"

"What is step two, dobe?"

Rubbing the back of his neck, the blond quickly glanced at his notebook, looking to where he had written all the steps down. "Step two, acetylcholine is released."

"Right."

"And?"

Grinning, Sasuke pulled Naruto towards himself and kissed him on the side of the mouth. Eyes closing, the blond reveled in the feeling of Sasuke's mouth on his skin. He shivered delightfully as an ivory arm wrapped around his waist and pulled him closer, creating pleasant friction.

"Dobe," Sasuke murmured as he kissed a smooth chin, "Think. How did we do step two?"

Groaning, Naruto's hands came up to tangle in Sasuke's hair as a devilish tongue licked its way to his ear. Another pleasant shiver coursed through his body before Naruto decided he wanted a taste too. Pulling away an inch, the blond cupped Sasuke's chin with both hands and kissed the warm red lips of his lover.

Just as fast as lightning, the answer came to him.

"Your tongue!" He blurted out, "W-When you opened your mouth, y-your tongue…it's like the assclean!"

Sasuke winced, "Acetylcholine, dobe."

"Yeah!" Naruto grinned, "Acetylcholine! When you opened your mouth, you released your tongue! Just like when acetylcholine is released…and then step three!" Stopping to take a breath, Naruto turned around. Step three. He remembered step three! "Step three, when you rubbed your tongue against mine…that was acetylcholine binding to the receptors, right?"

Nodding, Sasuke smirked, "Hn."

"Hell yeah!" Pumping his fist in the air, Naruto grabbed his notebook off the kitchen table and read off the next step, "Step four, ligand gated channels open. How you gonna open my ligand channels, teme?" Naruto said, wiggling his eyebrows.

Rolling his eyes, Sasuke grabbed the blond by the sleeve of his shirt and started pulling him out of the kitchen. Smiling ear to ear, Naruto let himself be led up the stairs and down the hall towards his room where they stopped in front of his closed door.

"Well?" Naruto inquisitively asked, wondering how Sasuke was going to make him remember the next step.

"Open the ligand gated channel, dobe."

"The door?"

"No, your face."

Letting Sasuke's remark slide, Naruto bit his lip in excitement and threw the door open, rushing into the room. Sasuke followed in suite slowly behind him, walking over to the light switch beside the doorway.

"Step five," he turned on the lights, dimming them to the perfect setting, "Opening of the voltage gated channels." Then stepping towards his lover, the Uchiha grabbed Naruto's arm to keep him from removing his shirt. Confused, blue eyes looked up questioningly into globes of ash. He was just about to ask Sasuke why the other teen was hindering them when the older boy pushed him firmly towards the bed. Stumbling, Naruto backed up, falling to the bed in a sitting position.

"Sas–"

"Shh," the older boy whispered as he bent his head down to kiss a lightly bronzed neck. A pleasant shock coursed its way through Naruto's body as Sasuke's tongue ran down to his jugular and back up. He let a pleased sigh escape his lips when he felt the Uchiha's warm palm come to rest on his thigh. Slowly it began to move up and down, creating a wonderful array of heat. With each movement of Sasuke's hand, the tightness in his stomach increased and when the raven's hand ventured further, Naruto let out an excited groan.

Sasuke let out a quiet chuckle as he rubbed his boyfriend through the coarse denim jeans. Beneath his fingers, he could slowly feel the effects of arousal take on a more physical form. While his hand tugged and stroked his lover into hardness, his lips worked their magic on a spot directly below Naruto's ear. Sucking hard, Sasuke released the blonde's neck, licking his work of art with a satisfied hum.

"S-Sasuke," Naruto groaned as his head fell back, an action caused by one particular stroke of the clever Uchiha's hand, "Stop teasing me, you bastard."

Looking up, Sasuke raised one fine eyebrow, "I'm not teasing you. I'm making you learn."

"This is teasing, teme."

"Remember that excitement from downstairs?" Sasuke licked his night's masterpiece once more, "Where is it now?"

Naruto groaned in annoyance, "Damn it, Sasuke! I can't think!"

"Why?" The raven asked knowingly.

Letting out a snort, Naruto supplied his boyfriend with an answer, "I'm hard, bastard. It's difficult to think when all I want to do is rip off your clothes…"

"And that's step six."

The blonde paused, not quite seeing it, "How?"

"That action potential from step one," Sasuke smirked, lifting his head to kiss Naruto's parted lips, "Has now gone straight through to your T tubules."

"My T tubules?"

An exasperated sound escaped Sasuke's mouth as he pulled away and stared crossly into his lover's eyes. Then purposefully he pushed his knee into Naruto's groin, "Your dick, moron."

Swallowing thickly the blonde shifted on the bed, eyes still locked with those of the Uchiha. Slowly he reached towards Sasuke, a firm hand coming to rest on the raven's shoulder as Naruto leaned in with his body, bringing himself closer. He licked his lips anxiously before tilting his head to the side, "Teach me more."

Grunting, Sasuke closed the short distance between them and captured Naruto's lips again. He let his hands travel over the denim fabric of Naruto's jeans, rubbing his long fingers against the inseams. A quiet pleasant sigh escaped the blonde's mouth. Without further ado, Naruto began to tug on Sasuke's shirt, signaling the other that he was ready to let loose. Giving Naruto's bottom lip one last suck, the Uchiha reluctantly pulled his lips away, eyes glazed over with repressed desire.

He couldn't let his hormones run the show. Not just yet.

"Naruto," Sasuke said gruffly, lashes flickering closed as the blond latched onto his throat and began creating marks of ownership on his ebony skin. "The…next few steps…are going to come q-quick…so you have…to p-pay attention."

"Mhm."

"Ah," Hissing in pleasure, Sasuke threw his head back as Naruto's left hand rubbed him through his jeans, teasing him deliberately, just as he had done earlier. Almost simultaneously the two boys reached for their shirts, pulling them off in one fell swoop. Belts were discarded along with socks onto the dark carpeted floor. Naruto groaned loudly as Sasuke's tongue ran down his navel, flicking just along the pant line of his jeans.

Zippers were pulled down and buttons were undone.

Soon both boys were down to their briefs.

The only article of clothing left keeping them apart.

Sasuke hungrily attacked a bare nipple, sucking it into his mouth and letting his fire hot tongue circle the nub like a shark. Naruto arched his back, forcing his locks of blonde hair to become more familiar with the downy pillow he was currently resting on. A shaky hand reached out towards a nightstand as fingers trembled in effort to pull open the single drawer containing one deeply desired tube of lube.

Feeling Naruto's muscles move beneath him, Sasuke lifted his head just in time to see his boyfriend release the handle of the smooth oak drawer and reach in to grab a purple tube. Like a panther, Sasuke pounced on the lube, stealing it from Naruto's hand without much effort.

And before the blond could utter his protest, Sasuke silenced him by rocking his hips, effectively rubbing their erections together. A hiss escaped Naruto's mouth as his cock throbbed in a most frustrating fashion.

"Step seven," Sasuke grunted as he unscrewed the lid of the tube, "Calcium is released from the cisternae of the sarcoplasmic reticulum." He wiggled the tube in emphasis to make sure Naruto understood. "And step eight, Ca–"

Naruto cut Sasuke off, having remembered this step, "Calcium binds to troponin."

"Which is located where?" Sasuke said as he shifted atop the blonde.

Naruto grinned, watching Sasuke toss the cap onto the nightstand, "On actin."

"You're going to be actin, Naruto."

"Why?"

Smirking, Sasuke stood and pulled down his briefs exposing his rather large cock, "Because myosin is thicker…which _I_ happen to be."

"Wait!" Naruto's eyes widened, "I was bottom last time!"

"Your point?" Sasuke lifted one eyebrow questioningly.

"I-I…uh," Naruto swallowed as the dark haired raven pulled his hand forwards and administered a generous supply of the clear gel.

"Prep yourself, but keep the briefs on."

The blond looked up at Sasuke with a confused expression, "You want me to do it with my underwear on?" Scrunching his nose, Naruto looked down at himself then back at Sasuke. "How the hell am I supposed to do that?"

The older teen shrugged his shoulders.

"Teme," Naruto growled, though he couldn't keep the huskiness out of his voice when he spoke, "I'm taking them off."

"No," the raven stated firmly, "They need to stay on. They're part of step nine."

Frowning, the younger teen looked back down at himself, cheeks turning bright red as he imagined himself looking ridiculous before Sasuke's eyes. Nervously, he looked back up at his boyfriend. "You can't look."

"Hn."

"I'm serious, Sasuke!" Naruto licked his lips before glancing down at his clothed erection, "It's embarrassing…"

Sighing, Sasuke turned his naked back to his boyfriend, conceding to the blonde's wish. Once Naruto was sure the raven wasn't going to look, he rubbed the lube between his fingers before raising the band to his briefs. Carefully and slowly, he reached towards his anus. Hissing slightly when the cold gel touched his heated flesh.

Expertly he inserted a single finger into the tight ring of muscles, gently pushing it in before slowly pulling it out. He grunted as he slipped another digit in, his movements becoming a little quicker as he was anxious to finish.

Unknown to the blond, Sasuke had turned his head back around and was now staring carnally at the tantalizing display before him. Unable to help himself, he gripped his erection with his whole hand, pulling it as he watched Naruto squirm on the mattress. Groaning silently, he witnessed the blond lift his bare back off the mattress. Licking his lips, Sasuke pulled roughly on his cock, letting the sweet friction engulf him in its delicious heat.

Feeling he was ready for his next lesson, Naruto pulled his hand out of his underwear and collapsed his head onto the pillow. Breathing in a large breath of air, he closed his eyes, horny and excited. "I'm ready," he called.

Within seconds Sasuke was atop of him, kissing him as if he'd been denied that particular pleasure for weeks. Naruto moaned into the searing kiss, wrapping his arms around Sasuke's moon graced back in order to bring him closer. Gladly the raven pressed closer, letting his chest rub against the blonde's.

"W-what's n-next, S-Sasuke?" Naruto breathed out as the Uchiha ran his tongue down his neck. Remembering he was supposed to be teaching his boyfriend about muscle contraction, Sasuke lifted his head, onyx orbs staring lustfully at Naruto's flushed face.

"Step nine," Sasuke's velvety voice rumbled before catching rosy lips in a chaste kiss, "Exposure of the active site on actin." With one practiced tug, the Uchiha held Naruto's briefs in his hands, effortlessly tossing them to the carpeted floor beneath. Leaning down, Sasuke ran his tongue over the feverishly hot skin shielding Naruto's sac from the outside. A strangled cry escaped the blonde's lips as the muscles in his legs shook from their short spasm. The neurons in his body fired at an alarming rate as Sasuke's tongue circled the sensitive skin.

Chuckling, Sasuke lifted his head just enough so Naruto could see his mouth, "Now for step ten, we need to hydrolyze some ATP."

That being said, the Uchiha leaned back down and nearly took in all of Naruto's length into his mouth. The blonde gasped audibly, nonsense spilling from his lips in blissful waves as Sasuke's mouth sucked him hard. Fists tightened in the sheets covering the bed as Naruto felt Sasuke's devil like tongue circle the head of his dick, willing cum to spring forth. Truth be told, the raven didn't have to wait long before he felt the warm salty liquid mingle with his saliva. Smirking to himself, he deep throated Naruto once more before releasing him.

The blond groaned loudly, wanting nothing more than for Sasuke's mouth to be wrapped firmly around his throbbing cock.

"Tell me, Naruto," Sasuke said as he climbed atop his lover, "Do you know what a cross bridge is?"

The blond shook his head.

Sasuke grinned lecherously, "Well, I doubt you will ever forget after this. Step 11." Positioning himself at the front of Naruto's entrance, the raven gave his lover a humorous look, "When actin and myosin bind."

Thrusting forwards, Sasuke pushed through the ring of muscles, gasping audibly as Naruto's heat enveloped him. The blond grit his teeth, pain shooting up his spine at the clear intrusion into his body.

"Fuck, Sasuke!" He glared venomously at his boyfriend, "What the hell? That hurt!"

"But you'll remember it." Sasuke reminded.

"Yeah," Naruto growled sourly, "And I'll also remember to whip your sorry ass after!"

Rolling his eyes, the Uchiha bent down and pressed his lips to a sweaty forehead, "Does it still hurt?"

"Not really," Naruto fidgeted a little before looking up at Sasuke, signaling him that it was okay to move.

"Step 12," Sasuke said a little more quietly, "The power stroke."

"Which is?" Naruto inquired.

Instead of answering him, Sasuke thrust his hips forward.

"AH!" Naruto's eyes rolled into the back of his head as his whole body shivered wantonly from Sasuke's single movement. Again Sasuke plunged in, hitting Naruto's prostate with deadly accuracy or rather…from a lot of practice. Nonsense once again flew freely from the blonde's mouth as euphoria washed over him with each and every stroke.

Sasuke pushed deeper, grabbing hold of Naruto he forced the blond into a sort of sitting position. He thrust harder and faster, causing Naruto to somewhat bounce in his arms. That friction he was creating had no words to describe it. It just felt so damn good, he never wanted it to end. With each forward thrust of his hips he could hear his ball sac hit against Naruto's ass, generating a smacking sound that drove him crazy with desire.

"U-ugh…" he grunted as he drove his cock deeper into the welcoming heat.

"S-Sasuke!" Naruto panted, cheeks flushed candy red as his erection rubbed eagerly against Sasuke's hard stomach, "F-Fuck m-me!"

With a wild look in his eye, Sasuke thrust faster, "You like cock, d-don't you, Naruto?"

"Yes!" Naruto gasped out as Sasuke's dick pushed against his prostate once more.

"You do," Sasuke pushed his hips forward again, "You love c-cock in y-your ass."

Throwing his head back, the blond screamed out, "Yes!"

Grinning like mad, Sasuke squeezed Naruto's ass firmly as he delved inside, letting him milk his dick for all he was worth. The room was filled with heavy panting and the primal sound of sweaty skin slapping together. All in all pushing both boys to the last stage of completion.

"S-Sasuke," Naruto managed in between pants, "I'm g-going to c-cum."

Nodding, Sasuke caught his lover's eye, "Me too."

With two more deep thrusts, the blond fell over the edge, his cum spurting onto Sasuke's stomach as a cry echoed off his lips. The raven was seven strokes behind, spilling his seed within the blond two minutes later. Together they collapsed on the bed, completely spent of all energy.

Slothfully Sasuke pulled out of Naruto and grunted before lying down next to his boyfriend, "Step thirteen, dobe."

"Mhm," Naruto hummed, eyes closed.

"Relaxation," Sasuke continued, "The cross bridge breaks." Closing his eyes, Sasuke pulled a half asleep Naruto into his arms before snuggling with him and letting his dreams take him.

:::

"Shit," Kiba growled as he sat down beside Naruto at lunch, "I can't believe I have to take summer school. This blows…well at least you'll be with me, so it won't be _that_ bad."

"Nope," Naruto grinned, taking a swig of his orange soda, "I got a ninety-five."

Shikamaru, Choji and Kiba stopped what they were doing and looked at the blond in what only could be described as shock.

"You," Kiba stammered, "Got an A?"

"That simply defies all logical explanations," Shikamaru said before yawning and turning back to his lunch.

"How did you beat me?" Choji asked in amazement, "You never beat me!"

"Well," Naruto grinned, "Let's just say that Sasuke found a method that insured I couldn't forget."

Shikamaru froze, his head turning to look from Naruto to Sasuke who was sitting a few tables down. As if feeling someone looking at him, Sasuke turned around, eyes catching those of a disbelieving Shikamaru. A bastardly smirk graced his features before the Uchiha turned around.

Turning back to his food, Shikamaru crossed his brows and wrinkled his nose before uttering under his breath, "How troublesome."

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**Hoping that wasn't extremely confusing.**

**It helped me study ^^;**

**Leave a review!**

**Oh and I made a twitter account. The link to it is on my devART homepage. There is a link to my devART page on my profile. I will be giving you guys updates about fics and such through there, so FOLLOW ME!**


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